1. Field of the Invention
The present invention relates to a vehicle parking assist device for assisting a driver in his driving by use of an image obtained by taking a scene of an area around a vehicle.
2. Description of the Related Art
To drive a vehicle, e.g., automobile, in safety, the driver needs to look traffic conditions around the vehicle attentively. The driver constantly watches the environment of the vehicle and makes efforts to grasp environmental conditions of the vehicle, while driving the vehicle. When the grasping effort depends on only the sense, there is a limit in perfectly grasping the environmental conditions. The human visual sensation is very important in grasping the environmental conditions. However, it is effective only in a direction in which the driver looks. The driver must drive the vehicle under the condition that areas that are shaded by the vehicle and from driver's view, i.e., the dead spaces, inevitably exist.
Major dead spaces as viewed from the driver are areas near the wheels and just before and after the vehicle body. In the dead spaces near the wheels, the driver cannot check the orientations of the wheels per se whose running directions change in accordance with a turn of a steering wheel. The steering wheel may be turned by plural turns in one direction. Accordingly, if the steering wheel is apparently at a neutral position, it is unknown whether or not the wheels are oriented for a straight drive. Further, visibility is limited in the backward area of the vehicle, so that the driver takes much care when he backs the vehicle into a narrow space.
Particularly, the parking technique is one of the most difficult driving techniques when a normal driver drives a vehicle. In parking the vehicle, the driver must steer the vehicle so that the vehicle moves into a narrow parking space without touching of his car with another vehicle or an obstructive object or without being mired in a ditch. The obstructive object and the other vehicle which the vehicle driven by the driver may touch usually exist in an area existing within a dead angle when viewed from the driver. Accordingly, the driver must steer the vehicle while exactly grasping relative positional relationship of the vehicle body to other objects.
In the technique to park the vehicle, particularly, particular the technique to park the vehicle in a parking space between the adjacent vehicles of those being parked in a row in a back-to-front fashion (this parking will be referred to as a “series parking”) is one of the most difficult driving techniques when a normal driver drives the vehicle. In the series parking, the driver must back the vehicle into a narrow parking space and reversely turns the steering wheel. Further, since the driver backs the vehicle, a parking space in which the vehicle is to be parked is the dead space when viewed from the driver and the driver insufficiently knows the environment around the parking space. In this state, the driver must parks the vehicle in the parking space
A drive assist technique in which when the vehicle is moved backward, it is disclosed in JP-A-1-14700 that an image of the backward or sideward area of the vehicle and a predictive traveling path curve are displayed. In the background technique, a predictive traveling path of the vehicle, which is predicted depending on a steering angle in the vehicle, is laid over an image of the backward area of the vehicle. Therefore, the driver can check both the steering angle of the steering wheel and safety in the driving in the backward area. According to the drive assistance of JP-A-1-14700, a steering angle of a steering wheel is detected by a steering sensor, a predictive traveling path corresponding to a steering angle of the steering wheel when the vehicle backs is overlaid on the image picked up by the camera, and frames are depicted in a state that those are equidistantly arrayed along the predictive traveling path or a simplified vehicle is depicted, whereby the driver easily understands in sense the predictive traveling path.
A drive assist technique which detects a length of a parking space by various sensors, and assists the driver in his parking by use of the detection result, is disclosed in JP-A-7-44799. According to JP-A-7-44799, when the vehicle passes the side of a series parking space, the vehicle parking assist device measures the parking space, and calculates an amount of steering operation, a time of depressing the accelerator or a time of depressing a brake pedal by using the parking space information measured and vehicle information, and guides the driver for the series parking.
A drive assist technique for assisting the driver in his driving by use of an image produced by picking up a scene around the vehicle is disclosed in JP-A-10-283592, JP-A-10-257482, JP-A-6-255423, JP-A-239400, JP-A-5-143894, JP-A-7-192199, and JP-A-57-150044U.
According to JP-A-10-283592, based on three dimensional analysis of an image picked up by a camera, it is judges whether or not the self vehicle touches an obstructive object, and the driver is informed of the judgement result while at the same time displays a relation between the self vehicle and the obstructive object.
JP-A-10-257482 discloses the drive assist technique which seamlessly composes an image of the backward area of the vehicle, an image of the left side of the vehicle, and an image of the right side of the same, and displays the composed image.
JP-A-6-255423 discloses a drive assist technique which displays an image picked up by a camera together with a distance scale for the drive assist.
JP-A-4-23940 discloses a drive assist technique in which a camera, which may be horizontally turned over a range of 360°, is attached to the ceiling of the vehicle with the aid of a turntable, a scene in areas existing in desired directions around the vehicle are picked up by the camera, and the images thus picked up are converted and composed for ease of watching by the driver, and the resultant image is used for drive assist.
JP-A-5-14389 discloses a drive assist technique in which scenes of the areas in the front left, front and front right of the vehicle are picked up by three cameras, and varies the segmental display areas or windows of the screen on which the images from the three cameras are displayed, thereby effecting the drive assist.
JP-A-7-19219 discloses a drive assist technique in which when the vehicle passes though a narrow road, an obstructive object is detected from an image produced by picking up a scene of the frontward area, and a gap between it and the obstructive object, thereby effecting the drive assist.
JP-A-57-150044U discloses a drive assist technique in which when an abnormality occurs, the contents of a display by a display device is changed from the display contents for a normal mode to the display contents for a normal mode, thereby effecting the drive assist.
However, as in the drive assist technique of JP-A-7-44799, a length of the parking space is estimated on the basis of a detected distance, and the drive assist is carried out for a garage parking and a series parking. In this technique, an image of the dead space for the driver is not displayed for the drive assist. Therefore, the technique fails to completely remove an anxiety of the driver.
In the background art of the JP-A-64-4700, a three-dimensional display along a predictive traveling path is used for enhancing the illusion of depth of a predictive traveling path image. The technique to merely display 3-dimensional images equidistantly arrayed along the traveling path predicted on the basis of a steering angle or move them along the traveling path is almost ineffective in checking a possibility that the vehicle will touch an obstructive object located near the predictive traveling path, because the driver must judge whether or not a steering angle of the steering wheel is proper.
Moreover, the information display device for displaying the images, usually installed to the vehicle, must be mounted in a narrow space near the driver seat. Therefore, the screen of the information display device is not large. For this reason, when the driver watches the display containing the backward area and the predictive traveling path curve, and judges if the predictive traveling path is proper, it is difficult for the driver to exactly judge if the predictive traveling path is proper.
Where the technique, as disclosed in JP-A-7-44799, to merely make an exact measurement of the parking space is used, it enables the drive to check if the parking space is sufficiently large, but it can unsatisfactorily assist the driver in the driving operation, which is necessary for the advancing of the vehicle to the parking space. The publication of JP-A-7-44799 describes in detail the measurement of the parking space, and refers to only the instructions of the driving operations for parking that is given to the driver. However, specific instructions are unclear in the description of the publication.
The parking assist technique, as disclosed in JP-A-10-283592, which merely judges if the self vehicle touches the obstructive object from the three-dimensional analysis of the image, fails to effect such a parking assist as guide the vehicle to a predetermined parking space.
On summarizing the above, in the drive assist technique in which the image picked up by the camera is used for the drive assist, an image of the dead space for the driver is used for watching the dead space. Therefore, the driver may check the environment conditions around the vehicle by watching the image, and the driver may take a feeling of security. However, those related techniques do not always provide proper drive guide information having a simple construction.